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DOI: 10.1055/s-2008-1078662
Mild Lewis Acid Catalyzed Ring Opening of Nitro-Cyclopropanes
Contributor(s):Hisashi Yamamoto, Marina NaodovicUniversité de Montréal, Canada
A Mild Procedure for the Lewis Acid-Catalyzed Ring-Opening of Activated Cyclopropanes with Amine Nucleophiles
Org. Lett. 2008, 10: 2809-2812
Publication History
Publication Date:
22 August 2008 (online)
Key words
nickel - cyclopropanes - amines
Significance
Charette’s group has recently reported highly efficient methods for the preparation of racemic and enantio-enriched 1-nitro-cyclopropane-carbonyls (Org. Lett. 2003, 5, 2327; J. Am. Chem. Soc. 2005, 127, 18014). This account represents a further extension of their studies on the utility of those activated cyclopropanes. The method described here provides access to chiral nitro compounds under mild conditions without the erosion of the chirality in the starting molecules.
Comment
One of the most interesting points of this report is the effect of the relative strength of Lewis acid on the product distribution of the reaction. More specifically, highly Lewis acidic mono- and bidentate catalysts (Al, Sn, B) provide racemic cyclic (3) and acyclic products (2) (via pathways b and c). In contrast, mild Lewis acids like Ni(II) lead to highly enantio-enriched products (1), circumventing the formation of zwitterionic species (A and B) giving racemic products.